Brake



Dec. 21, 1937-. E. G. CARROLL BRAKE Filed May 18, 1952 2 Sheets-Sheet l H" M0 WY. m W mm a W 5 N Ev W8 5 M \& H6 6 7 M M Patented Dec. 21, 1937 UNlTED STATES BRAKE Eugene G. Carroll, South, Bend, lnd assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware A Application May 18, 1932, Serial No. 612,139

5 Claims.

This invention relates to braking systems, and is illustrated as applied to a hydraulic braking system.

One of the difficulties sometimes encountered 5 in hydraulic brakes is that of maintaining the fluid connections free of air and other gases. Failure to accomplish this. causes a resilient or springy transmission of energy from the master cylinder to the wheel cylinder. Where the by- 10 draulic braking system is maintained under atmospheric pressure, it is relatively easy for air to be drawn into the system, thus causing bubbles of air to become mixed with the liquid. During the braking operation this air may be compressed 15 thus causing a loss of effectiveness in the operation of the brakes.

One of the objects of this invention is to provide means for automatically maintaining the liquid in 'a hydraulic braking system under a 20 predetermined superatmospheric pressure.

A further object of the invention is to provide means operated by the engine for developing such pressure.

A further objector the invention is to provide 35 means responsive to speed of travel of the vehicle for developing such pressures.

One of the features the invention is the construction of my efllcient vacuum operated pump for building up pressures.

so A further feature of the invention is my wind pressure pump operative for building up pressures on the liquid in the hydraulic braking system.

Additional objects and features of the inven- 86 tion will be apparent after a reading oi the subjoined specification and claims and after a consideration oi the accompanying drawings in which:.

Figure 1 is a plan view of a chassis of an auto- 40 mobile equipped with a hydraulic braking system constructed according to my invention;

Figure 2 is an enlarged view in vertical section of the master cylinder shown in Figure 1;

Figure 3 is an enlarged view in vertical section 46 of the wheel cylinder shown in Figure 1;

Figure 4 is an enlarged view in vertical section of the vacuum operated pump and of the fluid reservoir shown inFigure l; and

Figure 5 is a view in vertical section of a 50 modified system for maintaining the liquid under superatmospheric pressure.

Referring in detail to the drawings there is shown in Figure 1 a chassis of an automobile provided with side rails l0 and 12, a front axle 86 H, a rear axle 18, front road wheels 48 support- (Cl. (so- 545) ing said axle I4 and rear road wheels 20 sup-- porting said rear axle [6. Each of the road wheels l8 and 20 are provided with a brake 22 adapted to be operated by a wheel cylinder 24 towhich liquid is supplied from a master cylinder 6 26 by means of conduits 28 and 29. The liquid in the master cylinder, wheel cylinder and conduits is maintained under pressure by a vacuum pump 30, which is connected by a conduit 3| with the engine manifold 32 and is in constant communication through conduits 33 and 84 with the master cylinder 26 and the reservoir 36.

The master cylinder 26 is provided with a plunger 38 having reversed. sealing cups 40 and 42 positioned adjacent to the rear end thereof and having a forward piston 44 provided with a sealing cup 46. The forward end of the cylinder 28 is provided with a two way check valve 48 weighted by a spring 50 which bears at one end upon the valve 48 and at its opposite end upon the cup 46. The cylinder 26 is formed just in advance of the cup 46 with a restricted port 52 communicating with a well 54 formed on the cylinder. It is also formed rearwardly thereof with a relatively large opening 56 normally 5 closed by the piston and also communicating with the well 54. The well 54 is provided with a cap 58 connected to the conduit 34.

The arrangement whereby the piston normally covers the port 56 prevents liquid held in the rearward portion 01' the cylinder from, spilling or splashing out no matter what may be the position of the master cylinder and no matter what direction the vehicle is travelling. It also minimizes evaporation from the piston recess no matter how long the actuation of the brakes may be delayed. I

It is to be understood that in the event of expansion of the liquid in the recess between the piston 44 and the cups -42 due to heat or other 40 causes, a portion of the liquid may escape forward through the ports in the piston 44 and deflecting the cup 46 escape into the forward portion of the master cylinder and thence may escape into the reservoir through the port 52. Also in the event of contraction of the liquid in the recess to a depreciable degree liquid may seep from the well 54, around the piston 44 into said recess.

The wheel cylinders 24 are each provided with 60 a pair of pistons 60. Each of these pistons is formed with a pair of annular grooves in which there are positioned a pair of annular cup packings 62 and 64 facing in directions opposite to each other. The pistons 60 are provided with u slotted projections 88 which are adapted to contact with each other and limit the inward movement of the pistons. Interposed between the pistons is a spring 88 which normally urges the pistons outwardly into contact with the shoes.

' The pump 80 comprises a thin sheet metal cylinder I0 provided with a cover 12' held upon the cylinder by means of a bolt 14 and a nut I8 secured to the upper end thereof. The bolt I4 comprises a tubular member 'I8.and a plug 80 threaded into the upper end thereof. The tubular member 18 may be filled with an absorbent material 82 for straining the air which is drawn from the pump by the engine. It is provided at its lower end with a fitting 84 open to the atmosphere through which air may flow in. It is provided intermediate its ends with a plurality of ports 88 through which air is admitted to the interior of the thin sheet metal cylinder 18. The plug' 80 is formed at its upper end with a relatively large longitudinal bore 88 which is connected to the conduit 8| and through which air is drawn out through the manifold 82. It is provided with intersectingbores 89 connecting the bore 88 with the interior of the thin sheet metal cylinder I0.

Within the thin sheet metal cylinder I0 there is also provided an annular piston 90 normally urged downward by a spring 9I and a pair of valve sleeves 92 and 94 controlled by the piston. The interior of the valve sleeve 92 is in constant communication with the space in the cylinder Ill surrounding the sleeve by means of ports 98 in the sleeve 92. Thus by means of the sleeves 82 and 94, the bores 88 and 89 are alternatively connected with the interior of the thin sheet metal cylinder I0. .8 latch is provided for positioning the sleeves at the desired points. It comprises one or more spring pressed balls such as 98 adapted to flt either in one or in the other of a pair of grooves 98 and I00 formed in the sleeve. Springs I02 and I04 are positioned between flanges on the sleeves 94 and 92 and between a flange on the sleeve 94 and the piston 90 respectively. A fitting I08 threaded into the lowerendof the pump is connected to the conduit 88 and cooperates with the conduit to connect the pump with the reservoir 88 and with the master cylinder 28.

The reservoir 88 is provided to hold the reserve supply of liquid. It is formed with a cap I 08 which is held in position by a bolt I08 and a nut IIO therefor. The bolt I08 comprises a tubular member III and a plug II2 therefor. The reservoir is provided with a piston II8 formed with ports H4 and having associated therewith a cup packing H8, The piston H8 is maintained under predetermined pressure by a spring H8, a portion of the liquid being maintained under the piston H8 and under the pressure of the spring H8 and a portion thereof being maintained above the piston II8 under atmospheric pressure.

The upper end of the bolt m is provided with a vented fitting I I8 which normally maintains the upper, portion of the interior of the reservoir under atmospheric pressure. The tubular member I II is provided with a plurality of ports such as I28 and I22 for filling the upper part of the reservoir and with a constricted port I24 for relieving the hydraulic system should any excessively high pressure be developed. It is clear that if hydraulic pressure is developed high enough to compress the spring H8 and to raise the piston II8 above the ports I24, liquid may escape from beneath the piston through ports I24 and thence through ports I20 so as to lower the pressure beneath the piston. The plug H2 is formed with a relative y large longitudinal bore I28 which is connected with the conduit 88 and through the conduit with the fitting I 04 and the well 54. An intersecting bore I28 connects the longitudinal bore I28 with the lower part of the reservoir 88.

In the operation .of this embodiment of my invention, liquid is introduced into the reservoir 88 through the tubular member III and the bleed openings 89 in the wheel cylinders are successively opened. Operation of the motor draws the air from the interior of the thin sheet metal cylinder I0, through the manifold 82, the conduit 8|, and the port 88. This causes the piston 90 to be raised against the pressure of the spring 9I and thus draws fluid through the ports 4 in the piston I I8 and past the cup I I8 thereof and thence through the bores I28 and I28, through the conduit 88 and the fitting I08 into the lower part of the thin sheet metal cylinder 10. As the piston 90 approaches its upper limit of travel, the spring I04 contacts with the lower end of the sleeve 94 and builds up pressure thereon until the pressure is sufficient to overcome the holding effect of the balls 98 in the groove 98. Thereupon the sleeve 94 is quickly moved to its upper position so that the balls 98 move into the groove I00 and so that the ports 80 are closed and the ports 88 are opened. Thereupon air passes freely through the fitting 84 and the ports-88 to the interior of the pump". Air under atmospheric pressure thus being admitted, the spring 9| forces the piston 90 downward until the spring I02 contacts with the flange on the lower end of the sleeve 94 and then builds up suflicient pressure to move the sleeve back to the position shown in Figure 4. Also, whenever the motor is stopped or the vacuum decreases, the piston 98 is moved downward by the spring 9| which is capable of exerting a pressure greater than atmospheric but less than twice atmospheric (e. g. 24 lbs.). The downward movement of the piston 90 whether by reason of the stopping of the motor, the decrease of vacuum, or the shifting of the valve 94, forces the liquid through the conduit 88 to the well 84 and thence through the port 82 into the cylinder 28. Thence liquid is forced past the twoway check valve 48 into the conduit 29 and to the wheel cylinders 24. Subsequent operation of the motor tends to draw further liquid from the upper part of the reservoir 88 and subsequent drops in vacuum pressure forces additional fluid into the master cylinder and wheel cylinder until the system is filled with liquid, all air being forced out through the bleed openings 89. Subsequent thereto by reason of increases and decreases in the vacuum exerted additional fluid forced down by the piston 90 causes the piston I I8 to beraised and places the liquid in the system under the pressure of the spring I I8 which is capable of exerting a pressure substantially equal to that of the spring 9|. Operation of the master cylinder causes the liquid under pressure to flll the rear portion of the master cylinder displacing any air trapped therein and causing it to rise to the reservoir and provide an additional resilient cushion therein. Subsequent operation of the motor tends to increase the pressure built up upon the liquid in the system until it reaches a value determined by the springs 9| and I I 8. If expansion of the fluid in the system because of heat creates a higher pressure the port I24 is uncovered whereupon fluid may be relieved from beneath the piston I I8 to the portion of the reservoir above said piston. This superatmospheric pressure in the system prevents air (which obviously is only under atmospheric pressure) g 9 ,102,888 i'romjbeing sucked in at theiw he'el cylinders, the rear of the. master cylinder and-"other more or less expose'd portions of the system. The reversed cupspositioned at eachv end oi the wheel cylin ders, a nd' at the-rear end oi' the master cylinder v aid in preventing air irom leaking in.

It istobe understood that aiter bleeding is accomplished-iandithe system is.v filled with liquid,

iurtheroperationfoithe pumping system traps a quantityoi liquid under-the pistons-Gland I I3 and this l'iquid is: thus under the pressure oi? the springs 3 i and I I35 This trapped liquid prevents either of'the pi'stonsmovingtol'their lowermost position and thus the sleeve 94' isnormally maint However, whe'nthe liquid level-beneath the pistons" in the reservoir."fandthecylinder 10 drops to a.

automatically ope'rated'to trap. more liquid under I tained in' its upper position closing the ports 89.

point adjacent thebottonrfthe 'pump is again the pistons.

It is to be further understood that though the strengths oi the springs 3| and H3 are equal 'pressin'g'the spring 91 while. the piston 3' reinitially, whenever the. piston 90- is raised commains at the bottom of the reservoir 36, as soon as air is admitted to the cylinder 10 the spring 9i being compressed exerts more force than the spring I I3. Thus when airis introduced through the inlet 84 and the ports 83, the piston 93 moves down forcing the piston H3 up until the two springs are again in balance.

In Figure 5 I have shown a modifled'iorm of my invention in which a reservoir 228 is connected with a conduit 234 which is adapted to be connected with a master cylinder (not shown) and has its upper end connected by a conduit 233 t with a pressure responsive device 230. The pressure responsivev device is provided with a piston 290 normally urged outward by a relatively light spring 29! and limited in its outward movement by a stop 292. At the end opposite to the con.- nection with the conduit 233 the device is provided with a funnel 2!. The reservoir 228 and the conduit 233 as well as the left-hand end of the cylinder 230 are normally filled with liquid. The conduit 234 leads from the lower end of the reser-. voir 223 to a master cylinder similarly to the con-'- nection described above for the conduit 34 of Figure 1. v

If the automobile is traveling, air pressure entering theiunnel 2M acts upon the piston 290 and thus develops pressure in the conduit 233 and in the reservoir 228 thusmaintaining the liquid in the system under pressure which is responsive to the speed of the vehicle in traveling.

It is to be understood that the above described made therein withoutv departing irom.' the spiritinder provided with :a, pair of spaced ports, one b'e'-'-' ing a rearward port and the other Laforwardport,

covering the forward port, said means comprising a piston formed-witha' recess whichrecessisnor-j but is at times moved'with' the Diston'to register .with the rearward-port; and including; apacking.

leased position registers with" one of saidports retracting strokeoi! the plunger allowscommunl? I rounding said tubular member and adapted'to pass I over said intersectingbore.

reservoir andformedwith. anin'tersectingbore;

. an annular 'pistonwithin saidreservoir surrounding. said tubular member and jadaptejd to pass'o've'r said intersecting 'bore, and Ea spring acting. upon embodiments of my invention are for the purpose. of illustration only and various changes may be and scope of the invention.

Iclaim: 1. In a hydraulic braking system a master cyla reservoir communicatingwithsaid'ports; ineansl I for normally covering one-oi. ports andfor 10 at times, uncoveringJsaidrearwardport and mally positioned rearwardly of both. of said: ports cup positioned in advance-of saidpistonand normally positioned intermediate said ports,-jsaid1pls'--Y ton having:portsthrougnwhicli liquid'fmay'flow on the ret ractile stroke.v oisaidjiston. Y20-- 2. Ina hydraulicbraking'system,ia rnaster-cyl-- inder formed with a. iorward'end 'and'a;=rearward 1 end, provided with a-pair of longitudinally spaced ports, a reservoir, communicating with-. said ports, and a 'plungerformed wi'th'a"recess which' when the'plunger isr'noved iorwardfirom its.re'.

and said 'plunger' having means which during the cation with theportion. of the cylinder ahead ot--30 said plunger and beingflprovidedhwith a forward? piston normally positioned "to j cover." the ."rearl ward of said ports.

3. In ahydraul'ic' brakesystenr' areservoinf central tubular member extending throngh iz said reservoir and formed with an int ersecting b'o're','s and an'annular piston within said reservoir sur '4. In a hydraulic brake system a reservoinh central tubular member, extending *through: said" said i piston.

I 5'. .ln1':a hydraulie brake system,;a'master cylinder-formed with a pairof inlet ports,i-a'*p iston in 'said cylinder; havinga ,fo'rward' head normally positioned rearward of one of said and covering the other said port and 'h'aving a head -p'ositioned rearwardly of -bothyof-saidports thus forming a chamber between the-heads, and means for moving said. piston so that-the forward head advancesin front oi. bother. said ports.

' G. CARROLL. 

